Easy Q's Ch 3-4 Flashcards
1
Q
- What are the intracellular and extracellular concentrations of K+, Na+, and Ca++ in a typical cardiomyocyte at a resting membrane potential of -90Mv?
A
a. K+ in: 150 mM / out: 4mM
b. Na+ in: 20mM / out: 145mM
c. Ca++ in: 0.0001mM / out: 2.5mM
2
Q
- What is a chemical gradient?
A
a. Concentration difference
3
Q
- What is the equilibrium potential for Na+?
A
a. +52mV
4
Q
- If the Em = -90mV, what is the net electrochemical driving force for Na+?
A
-142mV
5
Q
- What is the equilibrium potential for Ca++?
A
a. +134mV
6
Q
- If the Em = -90mV, what is the net electrochemical driving force for Ca++?
A
a. -224mV
7
Q
- In a cardiac cell, how much do the individual ion concentrations change when ions cross the cell membrane during depolarization and repolarization?
A
a. They change very little
8
Q
- Why is the Em close to the EK?
A
a. Because g’K is high in the resting cell, while g’Na and g’Ca are low
9
Q
- With an action potential, in general, how many ions move across the sarcolemmal membrane?
A
a. Relatively small amount
10
Q
- Which of these requires ATP in order to function?
A
a. Na+/K+-ATPase (NKA) pump, ATP-dependent Ca++ pump
11
Q
- Define the term electrogenic.
A
a. An ion pump that generates a net charge flow as a result of its activity
12
Q
- What are the two general types of ion channels?
A
a. Voltage gated channels: open and close in response to changes in membrane potential
b. receptor gated channels: open and close in response to chemical signals operating through membrane receptors
13
Q
- What is an action potential?
A
a. APs occur when the membrane potential suddenly depolarizes and then repolarizes back to its resting state
14
Q
- What is the action potential duration in a typical ventricular cardiac myocyte, and how does this compare to other muscles and nerves?
A
a. Typical nerve: 1-2ms
b. Skeletal muscle cell: 2-5ms
c. Ventricular: 200-400ms (cardiac myocyte)
15
Q
- What cell types exhibit the “fast response” action potential?
A
a. Atrial and ventricular myocytes, and Purkinje fibers
16
Q
- Do nonpacemaker cells have a true resting membrane potential?
A
a. Yes, it remains near the equilibrium potential for K+ because gK, through inward rectifying potassium channels is high relative to gNa and gCa in resting cells
17
Q
- What is the absolute refractory period?
A
a. The cell is refractory (unexcitable) to the initiation of new action potentials
18
Q
- What is the intrinsic depolarization rate of the SA node?
A
a. 100-110 depolarizations per minute
19
Q
- Define positive chronotropy and negative chronotropy.
A
a. An increase in heart rate is a positive chronotropic response whereas a reduction in heart rate is a negative chronotropic response
20
Q
- What are the mechanisms by which autonomic nerves alter the rate of pacemaker firing?
A
a. by changing the slope of phase 4, which determines the time required for phase 4 to reach threshold
21
Q
- How could these mechanisms increase or decrease the slope of phase 4?
A
a. Sympathetic activation of the SA node increases the slope of phase 4, increasing pacemaker frequency (positive chronotropy)
22
Q
- What neurotransmitter is released by the vagus nerve at the SA node?
A
a. Acetylcholine
23
Q
- What does the right vagus nerve preferentially innervate?
A
a. The sinoatrial (SA)
24
Q
- What does the left vagus nerve preferentially innervate?
A
a. AV node
25
13. Define systole.
a. Events associated with ventricular contraction and ejection
26
14. Define diastole.
a. The rest of the cardiac cycle, including ventricular relaxation and filling
27
19. What waveform on the ECG represents the initiation of atrial systole?
a. P wave
28
22. At rest, what percentage of ventricular filling is the result of atrial contraction?
a. 10%
29
25. During exercise at higher heart rates, what percentage of ventricular filling is the result of atrial contraction?
a. 40%
30
26. What causes the increase in atrial contractility?
a. Sympathetic nerve activation
31
27. What is “atrial kick?
a. Enhanced ventricular filling owing to increased atrial contraction
32
28. What is the “x descent”?
a. The small decline in atrial pressure following the peak of the a-wave
33
29. Define end-diastolic volume.
a. The volume of blood in the left ventricle at the end of ventricular filling
34
30. What is a normal value for end diastolic volume?
a. 120 mL
35
31. What is a normal end diastolic pressure?
a. 8mmHg
36
32. What heart sound is heard during atrial contraction?
a. Fourth heart sound, S4.
37
36. What waveform on the ECG represents the initiation of isovolumetric contraction?
a. QRS complex
38
37. Describe the state (open/closed) of all heart valves during isovolumetric contraction.
a. All valves closed
39
39. What heart sound is heard during isovolumetric contraction?
a. First heart sound S1
40
55. What heart sounds are heard during the rapid ejection phase?
a. No heart sounds
41
56. Describe the sound created by the opening of healthy heart valves.
a. silent
42
58. What ECG waveform occurs during the reduced ejection phase?
a. T wave (ventricular repolarization)
43
59. Describe the state (open/closed) of all heart valves during the reduced ejection phase.
a. Aortic and pulmonic valves open, AV valves remain closed
44
60. What happens to ventricular active tension and the rate of blood ejection during the reduced ejection phase?
a. Ventricular active tension decreases and the rate of ejections falls.
45
64. Describe the state (open/closed) of all heart valves during the isovolumetric relaxation phase.
a. All valves closed
46
65. What causes these valves to close?
a. The total energy gradient reversal
47
66. What heart sound is heard during isovolumetric relaxation?
a. Second heart sound S2
48
67. Define incisura.
a. Deep notch
49
69. What happens to ventricular volume during isovolumetric relaxation?
a. Ventricular volumes remain constant
50
72. Define ejection fraction and provide normal resting values.
a. The stroke volume divided by the end diastolic volume. >0.55 (or 55%)
51
73. What happens to atrial volumes and pressures during isovolumetric relaxation?
a. Continue to increase owing to venous return
52
79. What happens to atrial pressure as soon as the AV valves open?
a. Rapid fall in atrial pressures as blood leaves the atria
53
80. What is the “v wave”?
a. The peak of the atrial pressure just before the valve opens
54
81. What is the “y descent”?
a. The peak is followed by the y descent, as blood leaves the atria
55
82. What is the Third Heart Sound and when is it heard?
a. During ventricular filling
56
84. Describe the state (open/closed) of all heart valves during the reduced filling phase
a. .AV vales open, aortic and pulmonic valves closed
57
91. What are normal resting systolic and diastolic blood pressures in the ventricles, aorta, and pulmonary artery?
a. Left Ventricle: 120/8
b. Right ventricle: 25/4
c. Aorta: 120/80
d. Pulmonary artery: 25/10
58
92. What are normal resting pressures in the right and left atria?
a. Right atria: 4
b. Left atria: 8
59
101. What is the equation for cardiac output?
a. CO = SV x HR
60
102. What are the units for cardiac output?
a. mL/min or L/min
61
108. What are the best indirect measures of preload?
a. Ventricular EDV or pressure
62
109. Define compliance.
a. The ratio of a change in volume divided by a change in pressure
63
112. What does a steep slope in the compliance curve indicate?
a. Lower compliance (hypertrophy)
64
113. What does a flat slope in the compliance curve indicate?
a. Higher compliance (dilation)
65
What happens to ventricular compliance with an increase in ventricular pressure or volume?
a. Compliance decreases
66
116. How does ventricular hypertrophy affect compliance?
a. Decreases ventricular compliance
67
117. What is lusitropy?
a. Ventricular relaxation
68
What is the relationship between preload and passive tension?
a. Increasing the preload length from points a to c increases the passive tension
69
125. What is the relationship between preload and the rate of active tension development?
a. AS preload increases there is an increase in active tension up to a maximal limit
70
128. At what sarcomere length does maximal active tension occur in cardiac muscle?
a. 2.2um
71
133. What is the normal range of sarcomere length at which normal skeletal muscle can operate?
a. 1.3 – 3.5 um
72
134. What is the range of sarcomere length at which normal cardiac muscle can operate?
a. 1.6 – 2.2 um
73
143. How does venous pressure affect preload?
a. An increase in venous blood pressure outside of the right atrium increases right ventricular preload
74
146. How could heart rate affect ventricular preload?
a. Through its influence on filling time, heart rate and ventricular filling are inversely related
75
148. How can atrial contractility increase?
a. Sympathetic activation
76
153. Define afterload.
a. The load against which the heart must contract to eject blood
77
155. What is the relationship between aortic pressure and afterload?
a. The greater the aortic pressure the greater the afterload on the left ventricle
78
177. How would norepinephrine increase inotropy?
a. By stimulating the cardiac muscle with norepinephrine
79
187. How is inotropy related to the ESPVR slope?
a. A decrease in inotropy = decreased ESPVR slope
80
189. What is the equation for calculating ejection fraction?
a. EF = SV / EDV
81
190. What is a normal ejection fraction value?
a. > 0.50 (50%)
82
191. What is the most important means of increasing the inotropic state?
a. The activity of sympathetic nerves
83
196. What equation is used to calculate myocardial oxygen consumption?
a. MVO2 = CBF (CaO2 – CvO2)
b. Myocardial oxygen consumption = coronary blood flow (arterial - venous oxygen contents)
84
197. What units are used to express myocardial oxygen consumption?
a. mL O2/100 mL blood (or, vol % O2)
85
198. What is a normal value for arterial blood oxygen content?
.2 mL O2/mL blood
86
199. What is a normal resting value for myocardial oxygen consumption?
a. 8 mL O2/min per 100g
87
200. What is a normal value for myocardial oxygen consumption during heavy exercise?
a. 70 mL O2/min per 100 g
88
201. What would a normal value for myocardial oxygen consumption be if the heart were arrested?
a. 2 mL O2/min per 100g
89
203. Why is the rate-pressure product useful?
a. It can be measured noninvasively
90
204. What factors lead to an increase in myocardial oxygen consumption?
a. Increased heart rate
b. Increased inotropy
c. Increased afterload
d. Increased preload
